This invention relates to diamond compacts.
Diamond compacts, also known as polycrystalline diamond, are well known in the art and are used extensively in cutting, milling, drilling and other abrasive operations. Diamond compacts are polycrystalline in nature and contain a high diamond content. Diamond compacts may be produced without the use of a second or bonding phase, but generally contain such a phase. When such a phase is present, the dominant component of the phase is generally a diamond catalyst/solvent such as cobalt, nickel or iron or a combination thereof.
Diamond compacts are manufactured under elevated temperature and pressure conditions, i.e. conditions similar to those which are used for the synthesis of diamond.
Diamond compacts tend to be brittle and so in use they are usually bonded to a substrate, the substrate generally being a cemented carbide substrate. Bonding of the diamond compact to the substrate will generally take place during the manufacture of the compact itself. Diamond compacts bonded to a substrate are known as composite diamond compacts.
Diamond compacts and the substrates, particularly cemented carbide substrates, to which they are bonded, are not very corrosion resistant. It is an object of the present invention to improve the corrosion resistance of a diamond compact.
EP 0 714 695 describes a sintered diamond body having high strength and high wear resistance. The body comprises sintered diamond particles of 80 to 96 percent by volume and a remaining part of sintering assistant agent and unavoidable impurity. The sintered diamond particles have a particle size substantially in the range 0,1 to 10 microns and are directly bonded to each other. The sintering assistant agent includes palladium in a range of 0,01 to 40 percent by weight and a metal selected from iron cobalt and nickel. The diamond sintered body may be produced by precipitating the palladium on a surface of the particles and thereafter electroplating the iron, cobalt or nickel. An alternative method disclosed is to mix the iron, cobalt or nickel with the diamond powder having the palladium coated thereon. In one comparative example, cobalt powder is infiltrated into the diamond mass and is said to result in a product having unsintered portions and hence unsuitable.
U.S. Pat. No. 5,658,678 discloses a cemented carbide comprising a mass of carbide particles bonded into a coherent form with a binder alloy which comprises, as a major component, cobalt, and an additional component selected from one or more of ruthenium, rhodium, palladium, osmium, iridium and platinum. The cemented carbide is made by mixing the binder component with the carbide particles. There is no disclosure of the use of a cobalt/platinum group metal binder in the context of a sintered diamond product.
According to the present invention, a method of making a composite diamond compact comprising a polycrystalline mass of diamond particles present in an amount of at least 80 percent by volume of the compact and a second phase containing a diamond catalyst/solvent and a noble metal includes the steps of providing a cemented carbide substrate, providing a layer of diamond particles on a surface of the substrate, providing a source of diamond catalyst/solvent and noble metal, separate from the diamond particle layer, and causing the diamond catalyst/solvent and noble metal to infiltrate the diamond particles under diamond synthesis conditions producing a diamond compact.